The present invention relates to a rectifying circuit, and more particularly, to a rectifying circuit used in a DC(direct current)-DC converter for delivering power between two batteries which have different rated DC voltages, respectively.
Rectifying circuits each having a rectifying diode are applied for DC—DC converters. In cases where the rectifying diode turns off, the sum of reverse bias voltage inputted to the rectifying diode and the reverse recovery voltage are applied on the rectifying diode. This requires that the rectifying diode is designed such that its breakdown volt exceeds the sum of the inputted reverse bias voltage and the reverse recovery voltage.
One of methods of increasing the breakdown voltage of the rectifying diode is to make large the breakdown layer width having the low impurity concentration. This method, however, may cause the forward loss of the rectifying diode and the radiated noise for the reverse recovery time thereof, whereby to reduce the breakdown voltage of the rectifying diode as much as possible while keeping it within the allowed limits.
One of methods of making low the reacting diode's rated voltage is to connect a snubber circuit, which has a capacitor and a resistor connected to each other in series, to the rectifying diode in parallel thereto, which, as for example, has already been disclosed in Japanese Patent Publication No. H10-4680.
Adding the snubber circuit to the rectifying circuit causes its whole structure to be large-sized and its cost to increase.